Aqueous suspensions of pentabromobenzyl acrylate

ABSTRACT

Suspensions of PBBMA, characterized in that they comprise PBBMA in the form of finely ground particles and contain suspending agents chosen from among xanthene gums, anionic or nonionic purified, sodium modified montmorilonite, naphthalene sulfonic acid-formaldehyde condensate sodium salt, sodium or calcium or ammonium salts of sulfonated lignin, acrylic acids/acrylic acids ester copolymer neutralized-sodium polycarboxyl, and wetting agents chosen from among alkyl ether, alkylaryl ether, fatty acid diester and sorbitan monoester types, polyoxyethylene (POE) compounds.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a divisional of U.S. application Ser. No.09/878,802 entitled AQUEOUS SUSPENSIONS OF PENTABROMOBENZYL ACRYLATE,filed Jun. 11, 2001, which claims foreign priority on IsraeliApplication No. 136725, filed on Jun. 12, 2000, the disclosures of whichare incorporated herein by reference.

FIELD OF THE INVENTION

This invention relates to novel compositions of matter that are aqueoussuspensions of pentabromobenzyl acrylate (PBBMA) and to a process formaking them.

BACKGROUND OF THE INVENTION

Pentabromobenzyl acrylate (PBBMA) is an acrylic monomer, which is usefulin many applications, especially but not exclusively, in the field offire retardants for plastic compositions. It can be polymerized easilyby known techniques such as bulk polymerization, solution polymerizationetc., or by mechanical compounding or extrusion. In mechanicalcompounding or extrusion, it may be grafted onto existing polymerbackbones, or added to unsaturated loci on polymers.

All these properties render PBBMA a particularly useful tool in thehands of experienced compounders. However, it has been impossible, sofar, to carry out aqueous manipulations with PBBMA, in spite of theirdesirability, because, on the one hand, PBBMA is insoluble in water, andon the other hand, because of its high bromine content, it has a highspecific gravity, about 2.7,—and therefore does not lend itself to thepreparation and use of aqueous suspensions.

It is a purpose of this invention to provide stable dispersions orsuspensions of PBBMA, which are new compositions of matter. Dispersionsand suspensions are to be considered synonyms, as used herein.

It is another purpose of this invention to provide such dispersions orsuspensions that are aqueous dispersions or suspensions.

It is a further purpose of this invention to provide a process forpreparing such suspensions.

It is a further purpose of this invention to provide suspensions ofPBBMA for particular applications in industry.

It is a still further purpose of this invention to provide suspensionsof PBBMA together with additional compounds, such as synergists forincreasing the fire-retarding efficiency of compositions obtained fromPBBMA.

It is a still further purpose of this invention to provide processescomprising the polymerization and/or copolymerization of PBBMA for theproduction of particular products.

Other purposes and advantages of the invention will appear as thedescription proceeds.

SUMMARY OF THE INVENTION

The suspension of PBBMA, according to the invention, is characterized inthat it comprises PBBMA in the form of finely ground particles, having asize smaller than 50 μm and preferably smaller than 10 □m and morepreferably from 0.3 □m to 10 μm, and contains suspending agents chosenfrom among xanthene gums, anionic or nonionic purified, sodium modifiedmontmorilonite, naphthalene sulfonic acid-formaldehyde condensate sodiumsalt, sodium or calcium or ammonium salts of sulfonated lignin, acrylicacids/acrylic acids ester copolymer neutralized-sodium polycarboxyl, andwetting agents chosen from among alkyl ether, alkylaryl ether, fattyacid diester and sorbitan monoester types, polyoxyethylene (POE)compounds. The POE compounds are preferably chosen from among:

-   -   POE allyl ethers N—5; 10; 20;    -   POE lauryl ethers N—5; 10; 20;    -   POE acetylphenyl ethers N—3; 5; 10; 20;    -   POE nonylphenyl ethers N—3; 4; 5; 6; 7; 10; 12; 15; 20;    -   POE dinonylphenyl ethers N—5; 10; 20;    -   POE oleate—N—9, 18, 36;    -   Sorbitan monooleate N—3; 5; 10; 20.

Alkyl naphthalene sulfonates or their sodium salts.

N is the number of ethylene oxide units.

Said suspension is typically, though not necessarily, an aqueous one.

The suspension according to the invention may also include nonionic oranionic surface active agents or wetting agents, which can be chosen bypersons skilled in the art. For example, nonionic agents may bepolyoxyethylene (POE) alkyl ether type, preferably NP-6 (Nonylphenolethoxylate, 6 ethyleneoxide units) Anionic agents may be free acids ororganic phosphate esters or the dioctyl ester of sodium sulfosuccinicacid. It may, also, include other additives which function both asdispersing agents and suspending agents commonly used by skilled personslike sodium or calcium or ammonium salts of sulfonated lignin, acrylicacids/acrylic acids ester copolymer neutralized-sodium polycarboxyl,preferably naphthalene sulfonic acid-formaldehyde condensate sodiumsalt. The suspension according to the invention may also includedefoaming or antifoaming agents, which can be chosen by persons skilledin the art. For example, emulsion of mineral oils or emulsion of naturaloils or preferably emulsion of silicon oils like AF-52™.

The invention further comprises a method of preparing a suspension ofPBBMA, which comprises grinding the PBBMA together with wetting agentand preferably also dispersing agent to the desired particle size addingit to the suspending medium, consisting of water containing suspensionstabilizing agents, with slow stirring, preferably at 40 to 400 rpm.Grinding is preferably carried out with simultaneous cooling. The orderof the addition of the wetting agents, the dispersing agents and thesuspending agents is important.

Preserving or stabilizing agents such as Formaldehyde, and preferably amixture of methyl and propyl hydroxy benzoates, can also be added to thesuspension.

Typical size distributions of PBBMA both before grinding and as they arewhen present in suspensions according to the invention, are listedhereinafter. “D” indicates the diameter of the particles in μm and S.A.indicates the surface area in square meters per gram. “v” designatesvolume and 0.25 means 25% by volume. D (v, 0.1) D (v, 0.5) D (v, 0.9)Specific S.A. PBBMA before 2.40 19.34 58.20 0.3623 grinding PBBMA in0.36 1.54 6.62 2.2554 suspension

In an embodiment of the process of the invention, wherein suspensions ofPBBMA and additional compounds—such as fire-retardant synergists, e.g.fire-retardant antimony oxide (AO), the process comprises preparing asuspension of the additional compound in a way similar to thepreparation of the PBBMA suspension, and then mixing the twosuspensions, preferably by adding the suspension of the additionalcompound to a slowly stirred suspension of PBBMA, and continuingstirring until a homogeneous, mixed suspension is obtained.

The suspensions, in particular the aqueous suspensions, of the inventionare stable. When stored at room temperature, they are stable for atleast two weeks and preferably at least one month. Their stability maybe higher, e.g. three months or more. If they have to be stored at hightemperature, they should pass the “Tropical Storage Test”, at 54° C.,viz. be stable under such Test for at least one week.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following examples are intended to illustrate the invention, but arenot binding or limitative.

EXAMPLE 1 Preparation of a Suspension of PBBMA

A glass bead wet mill equipped with cooling jacket and continuous feedby a peristaltic pump, was utilized for grinding. PBBMA (750 gr) wasmixed with water (240 ml), NP-6 (Nonylphenol ethoxylate) (1 ml) andDarvan#1 (Naphtalenesulfonic acid formaldehyde condensate, sodium salt)(30 gr). The mixture was fed into the grinding beads mill over a periodof 25 min. The resulting slurry was stirred gently, mechanical bladestirrer, 40-60 rpm, and 10 ml of 1.5% Rhodopol 23, Xanthan Gum (CASN^(o) 11138-66-2) in water with preserving agents, 1% Methyl Paraben,methyl-4-hydroxybenzoate, CAS N^(o) 99-76-3 and 0.5% Propyl Paraben,propyl-4-hydroxybenzoate, CAS N^(o) 94-13-3, were added.

EXAMPLE 2 Preparation of a PBBMA-AO Suspension

A suspension of Antimony Oxide was prepared as follows. To a 3-literround bottom flask, fitted with a mechanical stirrer, were added water(240 ml), NP-6 (1 ml) (Nonylphenol ethoxylate), and Darvan #1(Naphtalenesulfonic acid formaldehyde condensate, sodium salt) (30 g).Finely ground antimony oxide, Ultrafine grade with typical averageparticle size of 0.2 μm-0.4 μm. (AO, 750 g) was slowly added under faststirring, 400-600 rpm. The stirrer was slowed, 50-150 rpm and a 1.5%solution of Rhodopol 23 Xanthan Gum (CAS N^(o) 11138-66-2) withpreserving agents—1% Methyl Paraben, methyl-4-hydroxybenzoate, (CASN^(o) 99-76-3) and 0.5% Propyl Paraben, propyl-4-hydroxybenzoate, (CASN^(o) 94-13-3) were added (115 ml).

The mixed PBBMA-AO suspension was prepared as follows. To a slowlystirred, 40 rpm, suspension of PBBMA (750 ml) at 25° C.-30° C., obtainedas described in Example 1, was added the AO suspension (250 ml) asdescribed above. After five minutes, stirring was stopped, yielding ahomogeneous mixture.

EXAMPLE 3 Preparation of a PBBMA-Styrene-Butylacrylate Terpolymer Latex

In a 0.5 L 4 necked round bottom flask fitted with mechanical stirrer,reflux condenser, thermometer, dropping funnel and Nitrogen inlet werecharged 1.4 gr SDS (Sodium Dodecyl Sulfate) and 100 mL of water. Theflask was immersed in an oil bath and heated to 70° C. with continuousstirring, 250 rpm, Nitrogen was introduced under the surface of theliquid. After 1 hr. the nitrogen inlet was raised above the surface ofthe liquid and 0.15 gr of K₂S₂O₈ were added. Five minutes later asolution of 15 gr Styrene and 15 gr Butylacrylate was added dropwiseover 30 min. The emulsion pre-polymerization was continued for another90 min. after which 6 gr of a PBBMA suspension (˜60% solids) were addeddropwise over 70 min. The polymerization was continued overnight.

A stable latex (stable for more than two month) was obtained.

The terpolymer isolated from this emulsion was characterized. Thebromine content was 7% and the glass transition temperature was 18.8° C.

EXAMPLE 4 Preparation of a PBBMA-Styrene-Acrylonitrile Terpolymer

In a 0.5 L 4 necked round bottom flask fitted with mechanical stirrer,reflux condenser, thermometer, dropping funnel and Nitrogen inlet werecharged 1.4 gr SDS (Sodium Dodecyl Sulfate) and 100 mL of water. Theflask was immersed in an oil bath and heated to 70° C. with continousstirring, 250 rpm, Nitrogen was introduced under the surface of theliquid. After 1 hr. the nitrogen inlet was raised above the surface ofthe liquid and 0.15 gr of K₂S₂O₈ were added. Five minutes later asolution of 18.2 gr Styrene and 5.8 gr Acylonitrile was added dropwiseover 30 min. The emulsion pre-polymerization was continued for another20 min. after which 8.5 gr of a PBBMA suspension (˜60% solids) wereadded dropwise over 40 min. A second portion of 0.15 gr of K₂S₂O₈ wasadded 3 hr. after the addition of the suspension was finished. Thepolymerization was continued overnight.

A stable latex (stable for at least one month) was obtained.

The terpolymer isolated from this emulsion was characterized. Thebromine content was 12.5%, the nitrogen content was 5% and the glasstransition temperature was 107° C. The molecular weight depends on thepolymerization conditions. In this particular case a Weight AverageMolecular Weight, Mw, of 1.2*10⁶ and Number Average Molecular Weight,Mn, of 422,000, was determined (in Dimethylformamide solution,calibrated with Polystyrene standards).

The suspensions of the invention are useful for a number ofapplications, and the way in which they are used and the resultingproducts, are also part of the invention.

Fire Retardants are commonly used in carpet-backings. However, the fireretardants of the prior art are not bound to the carpet, and aresusceptible to removal by dry cleaning. According to the invention, theaqueous suspension of PBBMA is applied to the reverse side of thecarpets and is polymerized by heating at temperatures above 130° C. Thisresults in a coating of PBBMA polymer, which is bound to the carpet.

In the prior art, fire retardants are used in the textile industry.However, they generally produce light scattering, because they are usedin powder form. According to the invention, the aqueous solution ofPBBMA, optionally with complementary components, is applied to textilematerials and penetrates into the fibers, and then polymerization iseffected by heating at temperatures above 130° C., thus polymerizingPBBMA and binding the resulting polymers to the fibers. Addition of freeradical initiating catalysts, the conventional polymerization catalystssuch as organic peroxides, e.g., benzoylperoxide, or other free radicalproducing catalysts, e.g., azobisisobutyronitrile, will shortenpolymerization time.

The PBBMA suspensions of the invention can be used to copolymerize PBBMAwith other monomers or grafted to polymers, in order to produceadhesives, which are also fire-retardants or other types of surfacemodifiers and binding promoters.

Likewise, the suspensions of the invention can be used to copolymerizePBBMA with other (meth)acrylate derivatives, such as butyl acrylate,methyl methacrylate or other monomers, to produce transparent plasticsof predetermined refraction indices.

Double layered particles can also be produced, according to theinvention, by adding another monomer, e.g. another (meth)acrylicderivative, to the PBBMA suspensions under polymerization conditions, toproduce very stable latexes. An example of such other monomers can be,for instance, aliphatic (meth)acrylates or hydroxyethyl acrylate.

The novel products obtained according to the invention, and theprocesses for their production, are also part of the invention.

While examples of the invention have been described for purposes ofillustration, it will be apparent that many modifications, variationsand adaptations can be carried out by persons skilled in the art,without exceeding the scope of the claims.

1. A process for the fire retardation of textile materials, comprisingapplying an aqueous suspension of pentabromobenzyl acrylate (“PBBMA”) tothe textile materials and polymerizing the PBBMA by heating attemperatures above 130° C., wherein the aqueous suspension of PBBMAcomprises PBBMA in the form of finely ground particles and containssuspending agents chosen from the group consisting of xanthan gums,anionic or nonionic purified, sodium modified montmorilonite,naphthalene sulfonic acid-formaldehyde condensate sodium salt, sodium orcalcium or ammonium salts of sulfonated lignin, and acrylicacids/acrylic acids ester copolymer neutralized-sodium polycarboxyl, anda wetting agent selected from the group consisting of alkyl naphthalenesuflonates or their sodium salts, alkyl ether, alkylaryl ether, fattyacid diester and sorbitan monoesters, and polyoxyethylene (POE)compounds.
 2. A process according to claim 1, wherein the wetting agentsare chosen from the group consisting of: POE allyl ethers N—5; 10; 20;POE lauryl ethers N—5; 10; 20; POE acetylphenyl ethers N—3; 5; 10; 20;POE nonylphenyl ethers N—3; 4; 5; 6; 7; 10; 12; 15; 20; POEdinonylphenyl ethers N—5; 10; 20; POE oleate—N—9, 18, 36; Sorbitanmonooleate N—3; 5; 10; 20; and Alkyl naphthalene sulfonates or theirsodium salts; wherein n is the number of ethylene oxide units.
 3. Aprocess according to claim 1, wherein the aqueous suspension issuspended in a medium consisting of water.
 4. A process according toclaim 1, wherein the PBBMA is in the form of particles having a sizesmaller than 50 μm.
 5. A process according to claim 4, wherein the PBBMAis in the form of particles having a size from 0.3 to 10 μm.
 6. Aprocess according to claim 1, wherein the suspending agent comprisesxanthan gums.
 7. A process according to claim 1, wherein the textilematerial is a carpet and the aqueous suspension of PBBMA is applied tothe carpet-backing before polymerizing the PBBMA by heating attemperatures above 130° C.